This invention relates generally to the field of spiral wound gasket assemblies.
As far as known, the prior art method of manufacturing spiral wound gasket assemblies has consisted of forming a spiral wound gasket ring having several outer, loose strips of metal and then manually positioning the gasket ring within an inner groove in a circular gauge ring by hammering on the gasket ring with a suitable hammer. With this prior art method, the circular gasket ring is formed on a mandrel from alternating layers of metal strip and insulating material strip and welds are formed in inner and outer portions of the metal strip to retain the layers in a ring. The insulating material is commonly asbestos but may be other materials. Usually three to four loose wraps of metal strip are provided on the outer periphery so that the outer diameter of the gasket ring can be varied some by cutting off some of the excess wraps of metal strip so that the gasket ring can be positioned into the inside diameter of the gauge ring. The loose wraps act as a spiral spring to retain the gasket ring in the groove. In practice, the loose wraps are tightly wound about the outer perimeter of the gasket ring by a worker and a gasket is positioned adjacent the groove. The operator may then tap the gasket ring into the groove with the loose wraps springing outwardly against the groove to retain the gasket ring within the ring. Also, because the insulating material such as asbestos absorbs humidity, and also because of variations caused during manufacturing, the outside diameters of the gasket rings may vary so each fit between a gasket ring must be individually in a gauge ring by the person making the assembly.
Such prior procedure requires skill on the part of the worker and is a tedious, time consuming operation that requires much hand labor. Since it is generally necessary to trim a portion of the excess metal strip to fit the gasket ring inside of the gauge ring, such metal is wasted and becomes scrap. The prior art procedure produces gaskets which generally vary in the tightness of fit between the gauge ring and the groove. While a tight fit is desired, such a tight fit is more difficult and takes more time to achieve with the prior art procedure.
Radially deforming of the prior art gasket occurs when the gasket ring is placed under its intended compression load. This is necessarily so since the diameter of the gasket ring including the loose wraps of metal strip must be less than the inner diameter of the gauge ring to permit inserting the gasket ring within the gauge ring groove resulting in some radial play between the gasket ring and gauge ring groove. Accordingly, the initial loading of prior art gaskets provided non-sealing radial expansion until the play was taken up whereby further loading resulted in axial compression of the gasket ring to provide sealing.